react-dot-visualization/test-transform-math.html at main · fronx/react-dot-visualization · GitHub

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<!DOCTYPE html>
<html>
<head>
  <title>ViewBox Transform Math Test</title>
  <style>
    body {
      font-family: monospace;
      padding: 20px;
      background: #f0f0f0;
    }
    .test-case {
      background: white;
      padding: 15px;
      margin: 10px 0;
      border-radius: 5px;
      border-left: 4px solid #4CAF50;
    }
    .test-case.fail {
      border-left-color: #f44336;
    }
    svg {
      border: 1px solid #ccc;
      background: white;
      display: block;
      margin: 10px 0;
    }
    .dot {
      fill: steelblue;
      stroke: #333;
      stroke-width: 0.2;
    }
    h2 { margin-top: 0; }
    pre {
      background: #f5f5f5;
      padding: 10px;
      border-radius: 3px;
      overflow-x: auto;
    }
  </style>
</head>
<body>
  <h1>ViewBox Transform Compensation Math Test</h1>

  <div id="tests"></div>

  <script src="https://d3js.org/d3.v7.min.js"></script>
  <script>
    // The CORRECT formula (thanks GPT-5!)
    //
    // Mathematical derivation:
    // ViewBox maps data coords p=(x,y) to pixels by: pixels = S(p - origin)
    // where S = viewport/viewBox ratio and origin = (x0, y0)
    //
    // We want: S2(G(p) - o2) = S1(p - o1) for all p
    // where G(p) = k*p + t is our compensating transform
    //
    // Solving: k = w2/w1, t = (x2 - k*x1, y2 - k*y1)
    function calculateCompensatingTransform(oldViewBox, newViewBox) {
      const [x1, y1, w1, h1] = oldViewBox;
      const [x2, y2, w2, h2] = newViewBox;

      // Scale: ratio of NEW to OLD viewBox size
      const k = w2 / w1;

      // Translation: new origin minus scaled old origin
      const tx = x2 - k * x1;
      const ty = y2 - k * y1;

      return d3.zoomIdentity
        .translate(tx, ty)
        .scale(k);
    }

    const testsDiv = document.getElementById('tests');

    // Test case structure:
    // 1. Show original viewBox with dots
    // 2. Show new viewBox (without transform) - dots should appear different
    // 3. Show new viewBox WITH compensating transform - dots should look identical to #1

    function runTest(name, description, oldVB, newVB, dots) {
      const testDiv = document.createElement('div');
      testDiv.className = 'test-case';

      const transform = calculateCompensatingTransform(oldVB, newVB);

      testDiv.innerHTML = `
        <h2>${name}</h2>
        <p>${description}</p>
        <pre>Old ViewBox: [${oldVB.map(v => v.toFixed(1)).join(', ')}]
New ViewBox: [${newVB.map(v => v.toFixed(1)).join(', ')}]
Compensating Transform: translate(${transform.x.toFixed(2)}, ${transform.y.toFixed(2)}) scale(${transform.k.toFixed(2)})</pre>
        <div style="display: flex; gap: 20px;">
          <div>
            <h3>Original (old viewBox)</h3>
            <svg id="${name}-original" width="200" height="200" viewBox="${oldVB.join(' ')}"></svg>
          </div>
          <div>
            <h3>New viewBox (no transform)</h3>
            <svg id="${name}-new" width="200" height="200" viewBox="${newVB.join(' ')}"></svg>
          </div>
          <div>
            <h3>New viewBox + compensating transform</h3>
            <svg id="${name}-compensated" width="200" height="200" viewBox="${newVB.join(' ')}">
              <g id="${name}-transformed"></g>
            </svg>
          </div>
        </div>
        <p><strong>Expected:</strong> Box 1 and Box 3 should look identical (dots in same visual position)</p>
      `;

      testsDiv.appendChild(testDiv);

      // Draw dots in all three SVGs
      dots.forEach(dot => {
        // Original viewBox
        d3.select(`#${name}-original`)
          .append('circle')
          .attr('class', 'dot')
          .attr('cx', dot.x)
          .attr('cy', dot.y)
          .attr('r', dot.r || 2);

        // New viewBox without transform
        d3.select(`#${name}-new`)
          .append('circle')
          .attr('class', 'dot')
          .attr('cx', dot.x)
          .attr('cy', dot.y)
          .attr('r', dot.r || 2);

        // New viewBox with compensating transform
        d3.select(`#${name}-transformed`)
          .append('circle')
          .attr('class', 'dot')
          .attr('cx', dot.x)
          .attr('cy', dot.y)
          .attr('r', dot.r || 2);
      });

      // Apply transform to compensated group
      d3.select(`#${name}-transformed`)
        .attr('transform', transform.toString());
    }

    // Test 1: Zoom in (viewBox gets smaller)
    runTest(
      'zoom-in',
      'Zooming IN: ViewBox shrinks from 100x100 to 50x50 (centered)',
      [0, 0, 100, 100],
      [25, 25, 50, 50],
      [
        { x: 50, y: 50, r: 5 },  // Center dot
        { x: 25, y: 25, r: 3 },  // Top-left
        { x: 75, y: 75, r: 3 }   // Bottom-right
      ]
    );

    // Test 2: Zoom out (viewBox gets larger)
    runTest(
      'zoom-out',
      'Zooming OUT: ViewBox grows from 50x50 to 100x100 (centered)',
      [25, 25, 50, 50],
      [0, 0, 100, 100],
      [
        { x: 50, y: 50, r: 5 },
        { x: 25, y: 25, r: 3 },
        { x: 75, y: 75, r: 3 }
      ]
    );

    // Test 3: Pan right (viewBox shifts, same size)
    runTest(
      'pan-right',
      'Pan RIGHT: ViewBox shifts right (x increases, same size)',
      [0, 0, 100, 100],
      [20, 0, 100, 100],
      [
        { x: 50, y: 50, r: 5 },
        { x: 30, y: 30, r: 3 },
        { x: 70, y: 70, r: 3 }
      ]
    );

    // Test 4: Combined zoom + pan
    runTest(
      'zoom-pan',
      'Zoom IN + Pan: ViewBox shrinks AND shifts',
      [0, 0, 100, 100],
      [30, 20, 50, 50],
      [
        { x: 50, y: 50, r: 5 },
        { x: 35, y: 30, r: 3 },
        { x: 65, y: 70, r: 3 }
      ]
    );

    // Test 5: Single dot at origin (edge case)
    runTest(
      'origin-dot',
      'Edge case: Single dot at origin',
      [0, 0, 100, 100],
      [25, 25, 50, 50],
      [
        { x: 0, y: 0, r: 5 }
      ]
    );
  </script>
</body>
</html>